Semiconductor device geometries continue to decrease in size, providing more devices per unit area on a fabricated wafer. These devices are typically initially isolated from each other as they are built into the wafer, and they are subsequently interconnected to create desired circuit configurations. Some devices are fabricated with feature dimensions of several tens of nanometers. Spacing between doped-semiconductor devices and conductive lines on a patterned wafer may be separated by spacings similar to feature dimensions, leaving recesses or gaps of a comparable size. A nonconductive layer of dielectric material, such as silicon oxide (SiO2), is typically deposited over features to fill gaps and electrically isolate features from one another in an integrated circuit.
Dielectric layers are used in various applications including shallow trench isolation (STI) dielectric for isolating devices and interlayer dielectric (ILD) formed between metal wiring layers or prior to a metallization process (PMD). A generic patterned substrate 110 is shown in FIG. 1 filled with silicon oxide 120-1. The patterned substrate 110 has a relatively open area to the right and a trench to the left. After depositing silicon oxide over the patterned substrate 110, the silicon oxide outside the trench is typically removed by a variety of techniques including chemical mechanical polishing (CMP).
The silicon oxide in the narrow trench is desirable and the silicon oxide in the open area to the right may or may not be desirable. Chemical mechanical polishing often removes one region at a different rate than another to the spatial pattern variation. In FIG. 1, the polish has penetrated into the open area more than the narrow trench, an effect known as dishing. Dishing is rarely desirable since the material in the open area is not completely removed nor is it flush with the level of the silicon oxide in the narrow trench. Process sequences need to be modified (e.g. costly steps must be added) in order to reduce or address the effects of dishing.
Therefore, a need exists for methods of depositing silicon oxide in narrow trenches while retaining additional control over the material left in open areas and wide trenches of a patterned substrate.